1. Field of the Invention
The present invention relates to an antenna for a portable radio device such as a finger-ring-type radio device which transmits signals concerning physical data of a person who wears the finger-ring-type radio device.
2. Description of Related Art
A wristwatch-type portable radio device carrying a slot antenna on its band is known. Such a slot antenna is described, for example, in the book titled "Analysis and Design of Antenna for Mobile Communication Device" (Authors: Ito, Matsuzawa and Naito; Section 5.2, Chapter 2; published in 1995 by Trikepps). However, the efficiency of such an antenna is not sufficiently high, and further improvement of such an antenna has been desired.